The present invention relates to a magnetic disk apparatus and a head-supporting mechanism for the magnetic disk apparatus and, more particularly, to an actuator for high-accuracy positioning of a head that performs the writing-in and reading-out of information in a predetermined position on a magnetic disk on which information is stored.
A voice coil motor has so far been used as an actuator for moving a magnetic head over a desired position on a disk. However, this method had its limits when positioning accuracy was to be improved.
Therefore, in order to ensure that a magnetic head performs higher-accuracy positioning, arrangements in which a second actuator for the fine adjustment of the magnetic head position is disposed between the voice coil motor and the magnetic head have been proposed.
For example, the construction of a second actuator described in JP-A-12-113615 is such that in a magnetic disk apparatus comprising a magnetic head that performs the writing-in and reading-out of information, a magnetic disk on which information is stored, an elastic member which supports the above head, a fixed member which supports the above elastic member, a first actuator for rough movement which moves the above magnetic head over a predetermined position on the magnetic disk, and a second actuator for fine movement which is disposed between the above first actuator and the above magnetic head, the second actuator is a sheet-like structure formed from one piezoelectric flat sheet having electrodes on the top and bottom surfaces and two or more polarized regions in the interior or a plurality of such laminated piezoelectric flat sheets, and the second actuator, which is the above sheet-like structure, is disposed so that the top surface or bottom surface of the second actuator bridges the top surfaces of the above fixed member and above elastic member or the bottom surfaces of the above two members.
Furthermore, the above second actuator is a sheet-like structure made of a piezoelectric material and comprises one piezoelectric flat sheet having electrodes on the top and bottom surfaces or a plurality of such laminated piezoelectric flat sheets. At least one of the above electrodes on the above top and bottom surfaces is separated into two or more portions. The above piezoelectric flat sheet has in the interior a non-polarized region and two or more polarized regions separated by part of the above non-polarized region and polarized in the direction of thickness of the above piezoelectric flat sheet. The above piezoelectric flat sheet is displaced in its in-plane direction by applying an electric field to the above two or more polarized regions within the above piezoelectric flat sheet in the thickness direction of the above piezoelectric flat sheet by using the above electrodes on the top and bottom surfaces of the above piezoelectric flat sheet.